fix(metrics): Expose Badger LSM and vlog size bytes. (#7488)

Expose the Badger metrics for the lsm tree size and vlog size.

* badger_v3_lsm_size_bytes
* badger_v3_vlog_size_bytes

dgraph/cmd/alpha/metrics_test.go

@@ -183,6 +183,9 @@ func TestMetrics(t *testing.T) {
 		"badger_v3_disk_reads_total", "badger_v3_disk_writes_total", "badger_v3_gets_total",
 		"badger_v3_memtable_gets_total", "badger_v3_puts_total", "badger_v3_read_bytes",
 		"badger_v3_written_bytes",
+		// The following metrics get exposed after 1 minute from Badger, so
+		// they're not available in time for this test
+		// "badger_v3_lsm_size_bytes", "badger_v3_vlog_size_bytes",
 
 		// Transaction Metrics
 		"dgraph_txn_aborts_total", "dgraph_txn_commits_total", "dgraph_txn_discards_total",

x/metrics.go

@@ -490,13 +490,13 @@ func NewBadgerCollector() prometheus.Collector {
 			"Total number of memtable gets",
 			nil, nil,
 		),
-		"badger_v3_lsm_size": prometheus.NewDesc(
-			"badger_v3_lsm_size",
+		"badger_v3_lsm_size_bytes": prometheus.NewDesc(
+			"badger_v3_lsm_size_bytes",
 			"Size of the LSM in bytes",
 			[]string{"dir"}, nil,
 		),
-		"badger_v3_vlog_size": prometheus.NewDesc(
-			"badger_v3_vlog_size",
+		"badger_v3_vlog_size_bytes": prometheus.NewDesc(
+			"badger_v3_vlog_size_bytes",
 			"Size of the value log in bytes",
 			[]string{"dir"}, nil,
 		),